I think the performances in TMP are a little stiff and remote, but also more particularised than what you see in later films. That's not to say the later films aren't enjoyable (ST V is pretty strong on this front), but TMP was very well-directed. It may be that they were trying a different aesthetic with the first film, even on the level of acting, and it didn't work as well as they hoped. But also notice that "The Big Three" are pretty much their old selves at the end of the film, suggesting that the starchy nature of the performances was deliberate, as the characters struggled to bring themselves back into alignment. Damaged and degraded for some, improved and remedied for others. That's the nature of subjective beliefs. I actually do enjoy the Meyer films (maybe TUC more than TWOK). But their various flaws/limitations are very manifest to me now, much more than when I first saw them. By contrast, TMP has only continued to get better.